Oscillation Analysis and Damping Control for a Proposed North American AC-DC Macrogrid

TL;DR

This paper investigates the stability challenges of integrating North American AC grids via a proposed MTDC macrogrid, developing models and controllers to analyze and mitigate oscillation risks for reliable interconnection.

Contribution

It introduces a detailed dynamic model of the MTDC system with inverter-based resources and designs wide-area damping controllers to enhance stability.

Findings

Identification of inter-area oscillation modes with poor damping

Effective damping controllers improve oscillation stability

Model-based analysis confirms mitigation strategies' effectiveness

Abstract

In recent years, several studies conducted by both industry and U.S. Department of Energy (DOE)-funded initiatives have proposed linking North America's Eastern and Western Interconnections (EI and WI) through a multiterminal DC (MTDC) macrogrid. These studies have explored the advantages and opportunities of the proposed configuration from the perspectives of capacity sharing and frequency support. However, the potential challenges of small-signal stability arising from this interconnection have not been thoroughly examined. To address this gap, detailed model-based simulation studies are performed in this paper to assess the risks of poorly damped inter-area oscillations in the proposed macrogrid. A custom-built dynamic model of the MTDC system is developed and integrated with industry-grade models of the EI and WI, incorporating high levels of inverter-based energy resources. Through model-based oscillation analysis, potential shifts in inter-area modes for both EI and WI, resulting from the MTDC integration are characterized, and modes with inadequate damping are identified. Furthermore, to mitigate the risks of unstable oscillations, supplementary damping controllers are designed for the MTDC system, leveraging wide-area feedback to modulate active power set points at selected converter stations. A frequency scanning approach is employed for data-driven model linearization and controller synthesis. The damping performance is evaluated under the designed operating conditions and selected contingency scenarios.